Archive for APRS

Can a Raspberry Pi 3B do a decent job as an APRS client, gateway and digipeater? That was the question I asked myself a week or so ago and have spent the last few days trying to come up with that answer as well as which application will do the best job.

Jan Volschenk ZS6VOL has successfully reproduced the W2DEN APRS Tracker at his home in Pretoria South Africa. it is the first documented reproduction of the Tracker. It was a bumpy road at first but after Jan modified a small portion of the code to handle his GPS and loaded the latest Arduino IDE and Teenstduino he quickly got it working.

Great work Jan…..

Here’s a picture of the Tracker on Jan’s breadboard. Note the GPS coordinates, it isn’t Florida!

While surfing the internet for APRS Automatic Packet Reporting System information, I came across and article, (there are Many), using an Android or Iphone smart phone. I have an unused Droid HTC and loaded an APP named APRSDroid. I also loaded an APP for my Iphone named PocketPacket.

The software I run on my home computer is aprsisce/32. This is the iGate into the APRS servers. The web site is http://aprsisce.wikidot.com/

You will need a passcode (Link to Information ) to run APRSISCE/32 as an iGate and attach to the APRS internet servers. A passcode and can be had following the link above and emailing to the software owner here aprsisce-owner@yahoogroups.com with your name and Call. They are fairly fast in responding. You can obtain a passcode on line here. An APRS passcode is issued by call and is good for all APRS gateway software.

With just the smart phone, and the loaded APP, connected to the internet or cell service, APRs tracking was possible. This is a track of my mobile station AJ4FW-7 on a trip about town. Tracking is accomplished back through the internet to the APRS servers and then plotted on the various computer APRS mapping. The progression of this project is to use a Bao-Feng radio with an interface cable Adapter as shown in this link: https://github.com/johnboiles/baofenguv5r-trrs connected to my IPhone. I have ordered the parts from the site and the components from www.mouser.com

I just happened to catch this photo while the Radio was Transmitting

I ordered the parts as specified in the references above, but they were way too small for me to do anything with. I could barely see them, (0603) let alone solder them. 0603 is the size of the components. I took a look at another project I had built with the same value components, and the components were listed as 1206, which is double the 0603 part number. They were at least large enough that with a magnifying glass I could solder them to the Printed Circuit Board. Lo and behold it worked the first time out of the box so to speak.

W2DEN’s APRS Tracker using a Teensy 3.1 Microcomputer

Background:

While interest in packet radio waned, hams held onto their APRS capability and hardware. With the ability to use smartphones as APRS trackers and displays, interest is now on the rise. This piqued my curiosity if it was possible to make an APRS tracker from simple, readily available components. Turns out the answer is “Yes’. many have already completed trackers using Arduinos, Raspberry PIs and Teensy microcomputers / controllers. After a ton of research I have settled on creating a tracker with the following attributes:

Cheap: Less than $100 including an HT.

Reliable: Should work first time, every time.

Reproducible: Anyone with a soldering iron and a USB equipped Windows computer should be able to recreate the unit..

Portable / small.

Universal radio connections: This may be a bit difficult but will try to move any radio specifics into the interconnecting cable.

Upgradable: No proprietary hard or software. Open source only. Well documented

This is NOT a Heathkit. Nor is it a ‘buy the kit and put it together’ project. You will have to buy or scrounge the parts. Plan a schematic layout and solder the components together. There are no surface mount parts but the lands can get small and getting it right is critical. Do some loading of the sketch into the Teensy. And, finally, you will need to figure out how to fit this into an enclosure of some kind.

There was a day, way back in the history of the ether, when such a warning would not have been needed. Everything was home brewed and shared circuits were not much more than scribbles on a sheet of paper, or perhaps the back of a napkin, most likely made of cloth. While this step by step is a little more modern than those days it still reflects on the, ‘that’s a nice design, let me make it my way’ of thinking.

If you follow along, do some homework, figure out the details of your Teensy Tracker and leave some sweat on the shop floor you will be rewarded with a great project that actually works. Who knows, maybe even spark the inventor’s fuse in you to continue on to other projects.

Let’s get going:

Hardware:

This project is built around Teensy 3.1 made and sold by PJRC. What’s a Teensy you ask? A Teensy is a micro-controller that is a cousin to the Arduino line of micro-controllers. A controller does not have an operating system, it only runs one program at a time. Not to be confused with a Raspberry PI which is a micro-computer that runs an operating system and can have multiple applications available at a time to run, just like your PC or tablet.

Here is a list of the hardware for this project. This will be a ‘living’ table as the unit evolves. Two columns on cost, one for what is needed to recreate the APRS tracker the other for ‘nice to haves’ (not included in the <$100 cost limit).

RS: radio Shack: most of these components are no longer available. Substitutes can be found at flea markets, on-line etc.

M: Mouser. part numbers are current at the time of the project.

L: Lowes

SF: SparkFun

Development Environment:

As an Arduino cousin the Teensy will run most Arduino software. It uses a modified Arduino IDE (Integrated Development Environment) system, called Arduino, to develop software, called a sketch, and to load it into the Teensy via USB. Even if you are not developing any software you need the IDE to load the APRS sketch into the Teensy.

Let’s load Teensyduino, the Teensy IDE:

PJRC goes through this step by step, follow the procedure here. We’ll embellish:

Step 1:

Follow the link to the Arduino site and download the appropriate file. Most likely the “Windows Installer”. Save the “.exe” file the run it to install the Arduino IDE.

Step 2:

Skip unless you are running Linux.

Step 3:

Select the appropriate Teensyduino Installer from the list above Step 1:. If you are running Windows OS also download the “Windows Serial Installer” under “Other Files”.

Run the serial_install.exe if you are running Windows.

Then run the Teensyduino installer.

Confirm:

You should now have the Arduino IDE icon on your desktop. Click it to open the IDE. Now click the Help / About on the menu. It should say Teensyduino with a version number such as 1.23

Test:

There is a very good tutorial on how to set up the Teensyduino IDE and run your first sketch called “Blink” located here.

Click on the link and follow the “Basic Teensyduino usage” tutorial.

NOTE: the latest Teensy v 3.1 has the LED on pin 13. The first line in the sketch should read: “int ledPin = 13;”

That’s about it…. you now have the IDE installed and have tested it with your first sketch.

This post will describe the circuit and code to make a simple GPS receiver. This will be the core of the GPS Tracker.

Teensy 3.1 GPS Receiver v.0.4

Breadboard Setup:

Plug the Teensy into the lower numbered end of the breadboard as shown.

Using short jumpers connect the Teensy GND pin to the “-” rail on the breadboard and the Vin to the “+” rail of the breadboard. You can add jumpers to connect the + rails on each side and the – rails. be sure not to cross them.

The GPS module does not fit into the breadboard. Solder 4 wires onto the GPS units VCC, GND, TXD and RXD pins. These will be used to connect the GPS to the breadboard.

Plug the TFT display into the breadboard as shown.

Connections:

Refer to the “Welcome to Teensy 3.1” card that came with your Teensy or follow this link to a similar diagram online.

GPS:

GND to breadboard “-” rail.

VCC to breadboard “+” rail.

RXD to Teensy TX1.

TXD to Teensy RX1.

TFT Display:

Looking at display side of the TFT with the pins on the bottom the pins are labeled from left to right:

TFT

VCC

GND

CS

RESET

D/C

SDI(MOSI)

SCK

LED

SDO(MISO)

Teensy

Vin1

GND1

D102

3.3V

D9

D11

D14

VIN3

D12

Notes:

connect to breadboard + and – rails.

The Teensy digital pins (Dx) are labeled in grey on the “Welcome” card with D0 starting next to the GND pin.

Copy the entire contents of the file and paste it into the new Teensyduino file you just created.

Compile and load into your Teensy.

If you have everything set up correctly the file should compile, load into the Teensy. The display should light up and in a minute or two display the GPS data similar to the picture above. (Note: recent updates have changed the display format slightly, your s will be similar.)

Pour yourself a tall cold one, if you made it this far you deserve it. It took me about 3 weeks to get this far…. I hope, with these instructions, you can get this running in a few hours.

W2DEN’s APRS Tracker to Radio Interface

OK… you should have your GPS up and running. The next phase is to make an interface (I/O) between the GPS and the radio. Hopefully this will be universal for most rigs. The initial design comes from interfaces for a Kenwood HT like the TH6a or a Baofeng. Both use similar dual phono plugs (3.5 and 2.5 mm) for their external mic, ptt and speaker connections.

Here’s the circuit:

NOTES:

2N222 LED switch is optional. TFT LED lead can be connected to Vin through a 100 ohm resistor

Thanks to the great DigiKey SchemeIt app ( Link ) that was used to create the this schematic.

PTT

Most published Arduino based GPS trackers use a MOSFET to key the rig. Based on soundcard interfacing in other posts here at N4SER we will go against the ‘norm’ and use an optical isolator. The reason is to isolate the rig from the computer (Teensy) to prevent ground loops. Ground loops can be an issue when two devices attached to each other are using different power supplies and can usually be eliminated by physically separating the devices using optical isolators and transformers.

Any attempt at a ‘direct’ PTT connection using a 2N222 transistor caused feedback most likely due to a ground loop. This was consistent with what was found construction a sound card interface.

. . . the radio and computer, be it a PC or a Teensy, must be isolated from each other.

Audio feed: Teensy to Microphone Connection

This circuit followed previous work on sound card to radio interfaces utilizing a 1:1 (sold as 600:600) ohm transformer for isolation, and a voltage divider to reduce the Teensy’s output to microphone levels. The resistor values were determined experimentally using the fabulous ‘Soundcard Scope’ by Christian Zeitnitz. There is the link to the web site. ( Link ) The voltage divider with a 3.3 v input, from the Teensy will result in a maximum output of 33 mV. This falls below the 80 mV maximum Kenwood specs for their microphone input. These values may need to be tweaked a bit but theses seem to produce a clean signal. A pot could be substituted for the divider and adjusted accordingly.

Squelch Detect: Speaker (radio audio) to Teensy

This circuit is optional added in v 2.02. In order to avoid transmission collisions it is a good idea to monitor the radio’s speaker output and only transmit when the radio’s squelch is not opened by a transmission from another APRS radio. This is accomplished by setting the radios’ squelch so other stations open (break) it and it silences the speaker output when no other radios are heard.

The Tracker ‘listens’ to the radio’s output and will only transmit when no other station is heard, the squelch is closed, the speaker is quiet. The level is a user adjustable field in the AX.25 menu.

The Squelch Detect can be disabled by setting the value in the menu to 0 (zero).

RJ-45; Some Information

The schematic above shows an RJ-45B connector to connect to the radio. This follows the previous post on a digital interface by KK7UQ (Link). Details on creating the actual Cat 5 cable can be found in the Digital Interface II manual (KK7UQ Interface manual). Using this scheme will allow you to use the same cable for digital modes such as PSK using the ditial interface or as an APRS tracker. Another advantage to the RJ-45 is that there are 4 pins open for additional connections, perhaps the radio’s audio out for a speaker in the APRS tracker or a squelch control for transmit.

NOTE: be sure and wire this as a RJ-45B with Org / Wh as pin 1 and Org as pin 2. There are lots of websites explaining the difference between the A and B RJ45 wiring scheme.

Of course other jacks can be used here. An 1/8″ stereo jack with the mic and PTT ground connected will work just fine.

The APRS Tracker to Radio Cable

Cat 5 568 A & B

To use the RJ45 radio interface jack you will need a piece of Cat 5 cable with an RJ45 plug on one end.

Take an old cable and clip off one plug or cut one into whatever length you want or make your own if you have a crimper. Just keep the length under 24 inches.

Here’s how to connect it to the radio:

Determine if RJ45 plug is wired as an A or a B :

The plug will have 8 wires. One end will always be brown, the other end determines if it is A or B.

Orange / White it is a RJ45B

Green / White it is an A

the T568A / B is the EIA standard designation for the plugs.

Wire the ‘cut’ end as follows:

RJ45A

RJ45B

Radio

Grn/Wht

Org/Wht

PTT Ground

Grn

Org

PTT +

Blu

Blu

Mic +

Blu/Wht

Blu/Wht

Mic –

Brn

Brn

Speaker +

Brn / Wht

Brn / Wht

Speaker –

Teensy Tracker to Radio examples:

We’ll assume that the Cat 5 cable you are using is wired on the Tennsy tracker end as a B connection. The first pair is Orange, Orange / White. If you are using “A” wired cables then substitute Green, Green / White for the Orange pair.

Kenwood TH6a HT Also BoaFeng HTs

This has been tested on the Kenwood TH-6a. A 5 watt 3 band (144/220/440) HT.

Mic/speaker connection is a dual phono plug 1/8″ / 1/16″. This connector does not appear to be commercially available.

Assume a “B” cat 5 cable with the first pair being orange / orange/White.

Two separate phono plugs will be needed, 1/8″ and 1/16″. look for plastic or metal connectors with a recess, see below.

NOTE: The Kenwood dual jack connector has ‘collars’ around each connecor that fit into small indents in the radio around the mic and speaker jacks. This allows the OEM dual connector to fit tight against the body of the radio. Standard phono plugs may need to be trimmed to fit tight enough against the radio. If you find poor connections, mic plugs falling out or strange changes to the radio like changing bands then this may be your problem. The two connectors need to fit completely into the plugs. A light tug should not remove them.

This supposedly works on most BaoFeng HTs. Not sure about the recessed issue mentioned above but it should be considered.

Next will be some testing. Actually this has been ‘tested’ throughout the development but thought is would be easier to follow if every phase had its own post.

As is most packet related software this is a very old application that is still very popular.

This is very helpful if you do not have a local APRS gateway that can ‘hear’ your packets. From this location connection through the NI4CE gateway is very marginal so UI-View was set up as a local gateway.

To use UI-View you will need an operating packet station other than the Tracker connected to the computer that is running UI-View. An old PK-88 / 2M HT will work just fine.

Uses:

Observe the packet output of the Tacker and confirm that they can be received correctly.

Configure as an Internet Gateway to see your packets on aprs.fi (Google maps APRS app).

You must register UI-View in order to use it. Registration is free but a donation to a local cancer charity is requested, and a nice thing to do.

There are numerous websites with gory details on how to use UI-View so you will be spared those details here.

Note: your registration e-mail will contain the UI-View registration number and an APRS Server Validation number that will be used in the next step.

NOTE: The validation number is based on your call. There are numerous web sites that will generate the validation number. here’s one: ( Validation Link )

Initial Setup, under the Setup menu:

Station Setup: fill in your station information.

Comms Setup: Fill in the serial port of your TNC connected to the computer. Your elmer found it easier to use AGW PE, I’ll leave that for you to figure out.

To operate UI-View as an internet gateway:

Click Setup / APRS Server Setup

Under “Select One or More Servers” click the top server and then click the “Insert” key on your keyboard.

In the space that opened up type: rotate.aprs2.net:1458

Check APRS server log on required abd type in the APRS Server Validation number you received with your registration.

Check all three boxes under Gate RF to Internet

Here’s what it should look like, with your Validation number in place of the one shown:

Now connect to to the server:

Click: Action / Connect to APRS Server.

If everything is working correctly your call sign will show up in APRS.fi

. . . UI-View has a lot more capabilities. if you rae into Packet is an application worth learning.

Yahoo ! ! !

If the Tracker is working and your packets are being received by an APRS internet gateway your callsign, the one in the Tracker should show up on the Google APRS Map ( http://aprs.fi/#!lat=27.17990&lng=-82.38940 ) The link will show the Sarasota Fl area. Move around as needed.

Example Track

On a recent trip from Nokomis to Land O’ Lakes your elmer had the Tracker running on a breadboard into his Kenwood TM-281

There is a local track picked up by my UI-View server in the house and then by NI4CE when we got near Rt 75. Our packe

ts were lost somewhere south of our destination. As this was a breadboard setup it looks like a connection was intermittent. Things

will be better once this gets soldered.

The packets were sent out every 30 seconds. Hopefully this will become variable as the software is developed.

You can find this trace on APRS.fi by entering my Tracker call, W2DEN-5 and filtering the date to 6-26-2015.

The Tracker can be connected to the radio’s audio output (speaker, packet connector etc.) and it will monitor the audio level and only transmit when no signal is detected. This functions in connection with you radio’s squelch that must be set correctly. There is a 5 second time out that overrides this feature. A setting of 0 (zero) will disable this feature… the radio will transmit without checking the radio’s audio.

# of satellites

V+ monitor

Overall:

Universal radio I/O using Cat 5 cable.

Fully isolated from the transceiver

Sketches:

3 independent sketches (programs) were written for this project:

APRS GPS Receiver: This is a receive only sketch similar to the picture on top of Phase 2. (GitHub Link)

Don’t worry about GitHub, hopefully I will create a quickie primer on how to utilize it. For now download the ZIP file, lower right corner of the GitHub site and extract it into a folder named W2DEN_APRS_Tracker. It should then show up as a sketch in your Arduino IDE.

The HUGE box and the tape, will be replaced in the near future. 😕 There will be a post on construction when I receive the new box.

Main Screen ( Fig 1 ):

This will appear once the program has loaded and a stable fix has been established.

Updates every second. The Tracker will only transmit while this page is present.

Date

MM:SS

Date: corrected by UTC Offset

Count down until xmit

Time

MM:SS

Time: corrected by UTC Offset

Time between xmissionsSmartBeacon or constant

Latitude

Degrees Decimal Minutes N o rS

Longitude

Degrees Decimal Minutes E or W

Miles Per Hour

MPH. what else you need to know?

Heading

Heading, if moving

# of Sats

V+ check

# of birds heard

Warns below ~3.3v

Main Menu ( Fig 2 ) :

Fig 2 Main Menu

Push the button and you are graciously escorted to the Main Menu

Rotate the button to highlight an option

Push the button to go there

Return: back to the main screen

Send/Return: send a packet then return to main screen

User editable paramater Sub-Menus:

Packet: call signs, SSID etc.

AX.25: transmit delay, PTT/VOX etc.

SmartBeacon: Speed, rates, times

Display: On / Off ( not shown in Fig. 1 )

Packet Menu ( Fig 3 ) :

Fig 3 Packet Menu

Highlight Packet on the Main menu and push the button and you are delivered to the Packet menu.
Displayed are data you can edit and the current value. The data is stored in eePROM so is restored when the Tracker is turned on.

Of course this works the same way. rotate the dial to highlight and click to select.

Return: back to the Main Screen

UTC: offset to correct the GPS UTC time and date. This is only for the display. No DST correction.

Delay: time between transmissions if the SmartBeaconing is disabled. Time to first SB transmission.

W2DEN1: Your location call sign

SSID: Your location SSID

APRS1: Destination call sign

SSID: Destination SSID usually zero (0)

Car1: The symbol for your location Car, House etc.

Comment: 35 character comment transmitted with your packets.

Notes:

Your Tracker will show what you have set.

AX.25 Menu ( Fig 4 ) :

Fig 4 AX.25 Menu

This menu allows the setting of a number of parameters associated with the AX.25 protocol.

Xmit Dly: milliseconds between PTT and the packet flag transmission

# of Flags: The number of start byte flags (0x7e) (01111110) sent at the beginning of an AX.25 frame.

PTT Pin: Hardware pin on the Teensy used for PTT. Fro VOX set to 0 (zero).

Squelch: (not shown in Fig. 4) 0 to 1000. o (zero) disables the feature. The tracker will only transmit when the audio is below this level. You must set the radio’s squelch so APRS packets break the squelch. If the audio is not below this level the tracker will transmit after 5 seconds. Levels between 50 and 100 seem to work with most radios that were tested.

Smart Beacon Menu ( Fig 5 ) :

This menu allowss for full user control of all of the Smart Beacon parameters.

Enabled: Enabled turns the Smart Beaconing on. Disabled and the Tracker will transmit via the ‘ Delay’ setting in the packet menu.

fSpd: Fast Speed (MPH). At or above this speed and the tracker transmits at the fRate.

fRate: Fast Rate (seconds). Time between transmission when the Tracker is traveling at or above the fSpd.

sSpd: Slow Speed (MPH). At or below this speed and the Tracker transmits at the sRate.

sRate: Slow Rate (seconds). Time between transmissions when the Tracker is traveling at or below the sSpd. NOTE: When sSpd is active the current sRate will double after ever transmission until sRate is equal to or above the sRate then transmissions will be sent at the sRate.

tTime: Turn Time (seconds). The minimum time between transmissions due to a turn.

tAgle: Turn Angle (degrees). The minimum angle that will cause a turn transmission.

Slope: A calculated value based on speed, turn time and turn angle to compensate for speed.

There are a number of editors in the W2DEN Tracker menu that allow the above parameters to be edited. The following will describe how to edit these parameters.

Numeric / Symbol Editor ( Fig 6 ) :

Fig 6. Numeric Editor

The numeric parameters can be changed using the numeric editor. These include: UTC, Delay, both SSIDs, All AX.25 and Smart Beaconing parameters.

The APRS symbols; car, house etc. are also edited in the same manor a a number.

All numeric parameters have minimums and maximums set in the code.

Title:(UTC Offset) the top of the display will indicate which parameter you are editing

Now: Displays the current value

New: Displays the new value that will be stored.

Rotate the control knob to select the new value you want for the current parameter.

Push the control knob to accept the new value.

If the New = Now the value will not be changed.

The lower portion of the display will give you some additional information about the parameter.

Alpha Field Editor ( Fig 7, 8, 9 & 10 ) :

Fig 8. Call Editor Exit Select

Fig 7 Call Editor

The Alpha Field Editor allows compete editing of the Call fields (my call and Destination call) as well as the Comment field. Originally the call editor was different from the comment editor but the two have now been combined into a single, easy to use Alpha Field Editor.

Fig 9 Comment Editor

Explanation:

The display is in Landscape mode to handle the 35 comment characters.

The title ‘Comment’, ‘My Call’, ‘Dest. Call’ is on top.

Now: the current field contents.

Note: For the ‘Now:’ comment filed the last ( 35th) character is cut off so this all fits on the display

New: the new field with one character highlighted in white on blue.

To edit:

Rotate the control knob to highlight the letter to edit.

Push the control knob to select the letter. The letter will turn to yellow on blue.

Now rotate the knob to the desired new character.

Push the knob to change to the new letter.

repeat as needed.

Fig 10 Comment Editor

To save the new field contents:

Rotating the control knob past the end of the ‘New:’ field will display the ‘Exit’ choices:

Continue

Exit

Exit / Save.

Click to choose the one you want.

This new improved scheme for single control editing is far easier than the prior Call Editor.

—

User Defined Data:

Many published DIY APRS Trackers depend on hard coded constants to handle information such as UTC offset, Call, symbols etc. The W2DEN APRS Tracker 2 will store this data in EEPROM that is user editable via the menu system.

Note this uses the EEPROMex.h library

Here are definitions of these data:

Data

Byte

Type

Notes

Start

Length

check

0

1

char

* if data is present

UTC Offset

1

1

int8_t

Integer hours -12…14 (minutes to be added in the future)

dTime

2

2

uint16_t

unit: seconds: Time between transmissions (default)

source Call

4

6

String

A…Z, 0…9, / space padded char(32)

source Call SSID

10

1

int8_t

0…15 This is the call ID e.g. for a SSID of 5: W2DEN-5

dest. Call

11

6

String

A…Z, 0…9, / space padded

dest. SSID

17

1

int8_t

0…15 This is the destination call ID

Symbol Set

18

1

String

“\” or “/” for primary or secondary

Symbol1

19

1

String

various( – house, > car etc)

comment

20

34

String

a…z, A…Z, 0…9, some spec. chars. space padded

Fast Speed2

55

2

uint16_t

Smart Beacon mph 10 … 100

Fast Rate

57

2

uint16_t

Smart Beacon seconds 10 …600

Slow Speed

59

2

uint16_t

Smart Beacon mph 1 … 30

Slow Rate

61

2

uint16_t

Smart Beacon seconds 1000 … 5000

Min. Turn Time

63

2

uint16_t

Smart Beacon seconds 5 …, 30

Min. Turn Angle

65

2

uint16_t

Smart Beacon degrees 5 … 30

Turn Slope

67

2

uint16_t

Smart Beacon 200 … 300

axDelay

69

2

uint16_t

millisecond key down until packet starts

axFlags

71

2

uint16_t

integer # of ax.25 preamble flags ( 7e ) to send

axVoxOn

73

2

uint16_t

seconds VOX time on. 0 = use PTT

axVOXSilent

75

2

uint16_t

seconds VOX silent until first flag

pttPin

77

2

uint16_t

Teensy PTT pin # 0 = use VOX (normally = 13)

tftOnOff

80

1

int9_t

=1 for display on, =0 for off

squelch

81

2

uint16_t

0 – 1000 with 0 (zero) disabling the squelch feature

Notes: The user data is now functional.

The current Symbols are: house, car, motorcycle, balloon, sailboat, power boat, bike, truck, van, school. More can be added via programming as needed.

SmartBeaconing parameters.

References:

Some useful, for programing purposes, and perhaps interesting, for those who must know what goes on behind the scenes, information.

Up until now the APRS Tracker has been assembled on a breadboard in a rather large enclosure (see below). While convenient it is not very practical. So . . . lets put this into a small box:

Plan

Using a blowup of the RS PCB that would fit into the box, layout where everything will go / fit. This will take a bit of work to get the blowup to represent the actual board but will save time and perhaps your box when you start toe cut. Part of my blowup diagram can be seen under the box in the Fig 1.

Cut

Fig 1 PCB fit and Holes in box

(Fig 1) Once you have the layout finalized it is time to make some holes. A ‘Dremel’ tool with various bits will be a big help. Talk you time, Here are the parts placement and cuts:

Upper right: The black cube is the RJ-45 jack on the SparkFun PCB, tucked under the PCB. It will be glued to the Main PCB with the connections coming up through the PCB holes.

To the left is the USB Micro-B SparkFun PCB. This too will be glued to the Main PCB with some glue added around the actual connector for added strength.

On the left side is the GPS Receiver with the antenna cut through the box. While the antenna should face up it can be inside the box. It does look cool sticking out and will get protected with clear tape when finalized.

On the bottom is the push button rotary switch.

Add components (Fig. 2)

A 10 position stackable header has been added to accept the

Fig.2 GPS module and TFT Display jack

TFT Display pins. The height was adjuste with a small spacer at the bttom of the header. This puts the display at a good height to clear the RJ-45 jack and the transformers (still to come)

10 wires have been added to the header, the display only needs 9, to allow some flexibility in placing the display. This will be finalized before solder and the extra lead cut off one end or the other.

Two screws were added to hold the board in the box.

The RJ-45 jack on its Sparkfun PCB has been epoxied to the board.

The GPS unit is a tight fit at the top of the board behind the stackable header.

Now fit in the transformers etc.

Fig. 3 Wiring 101

Using the enlarged layout, visible below the W2DEN APRS Tracker carefully layout where the components will go. This will take some trial and error to fit everything into the case.

The two transformers and output voltage divider were fit in first.

The output is just above the RJ-45 connector, the input in the upper left.

The output voltage divider and by-pass cap are squeezed between the transformer and the RJ-45 Jack.

The input by-pass cap is soldered below the board.

The PTT socket fits nicely between the transformers.

The TFT Display 2N222A is wired directly to the D3 Teensy pin in the upper right.

Be sure to leave room for the rotary switch just to the left of the 2N222A.

The Tennsy is then fit with the USB wires feeding out the bottom.

They are soldered to the SparkFun USB Board (red, bottom center) which is then epoxied to the board. BE CAREFUL fitting it through the hole in the case.

Now wire the TFT stackable header to the Teensy.

Decide which 9 pins you want to use on the TFT Display Header and melt the unused on and cut off the wire.

Point to point is fine.

Create and follow a diagram.

Check you work with a pin header in the TFT header, then an ohm meter to confirm eac TFT header pin is correct.

Solder everything…

For the first pass just solder the Teensy Pins that are needed:

TFT Header, Output transformer

Two unused RJ-45 wires are coiled and left in the lower left corner, just in case we need them later.

Test #1

Plug in the TFT Display

Plug in the USB cable

The screen should light up and display:

W2DEN’s

APRS

Tracker Loading …

Finish it

Fig. 4 final

This is the final step. Wire the last components and put it into the box.

GPS:

The pins were removed from the GPS and replaced with 4 stranded wires (from an old USB cable).

The wires were then soldered to the board.

Rotary PB Switch:

the two grounds were connected at the switch.

The 4 connections were attached to the board using stranded wire, same as the GPS.

Place the board into the box and screw it down.

Insert the GPS module. A spot of glue or double backed tape may be needed, depends on how tight the fit is.

Insert the switch and secure it with the nut.

NOTE: the switch connections hit one of the display On/Off resistors. It is covered with a piece of wire insulation to prevent a short. (the white end of the insulation is visible to the left of the switch.)

Insert the 4N25 into the socket if you have not already done so.

YAHOO! You are done.

Plug in the USB cable and the tracker should light up and in a few moments connect to enough sats to show you the screen

Prototype Breadboard Enclosure:

Here is is the interior of the prototype in the RS box with the circuit on a breadboard.

The Teensy USB is hardwired due to the USB being broken from the board. Details are here: Link